syscall: enable ReadDirent tests on aix, linux and solaris

Change-Id: I13fd6bad4600ef909b13ac517ba6a06909b5c703
Reviewed-on: https://go-review.googlesource.com/c/go/+/182379
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/syscall/dirent_bsd_test.go → src/syscall/dirent_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly freebsd netbsd openbsd
+// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
 
 package syscall_test